Genetic, biochemical and biophysical methods will be employed to elucidate the chemistry interactions between DNA molecules in the formation of recombinants and the consequences of the presence of base-pair mismatches in recombinant structures. The investigation will include examination of the fate of both transforming bacterial DNA and transfecting viral DNA. BIBLIOGRAPHIC REFERENCES: Tiraby, G., M.S. Fox & H. Bernheimer (1975). Marker Discrimination in Deoxyribonucleic Acid-Mediated Transformation of Various Pneumococcus Strains. J. Bacteriol. 121: 608-618. Tiraby, J-G. & M. S. Fox (1974). Marker Effects in Pneumococcal Transformation, in Mechanisms in Recombination, Rhoda F. Grell (ed.), Plenum Press, New York, pp. 225-236.